We plan to continue working in the following areas: a) Determination of the effects of cannabis smoking alone and with alcohol on driving ability. the California State Department of Highway Safety will use their actual driving course for the testing. Subjects will receive cannabis in the form a cigarette and alcohol in the form of a flavored drink, or placebos for each, in four groups; b) Studies of the kinetics of THC in heavy versus light users of cannabis; c) Identification of neutral and acidic metabolites of THC in human urine (With stig Agurell, PH. D.); d) Improved analysis of THC-11-oic acid, the major urinary metabolite of THC; e) Identification of metabolites of THC in urine that may act as markers for recent use.